Liquid crystal display

ABSTRACT

A reflection electrode has an undulated shape and whose normal direction is distributed unevenly to a specific azimuth angle and whose reflection light intensity depends on said azimuth angle. Openings are formed in that area of the reflection electrode which has a tilt angle of 0 degree to 2 degrees and/or a tilt angle of 10 degrees or higher. The retardation of a liquid crystal layer is changed by making the liquid crystal molecular alignment mode different between the openings and the reflection electrode, so that the intensity of output light is increased in reflection mode as well as in transmission mode. The balance of colors displayed in transmission mode is determined by determining the area of the openings in pixels of each color, and the color temperature is set higher in transmission mode than in reflection mode. This provides a semi-transmission type liquid crystal display which has an excellent visibility in reflection mode as well as in transmission mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 10/214,250filed Aug. 7, 2002 (pending).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display, and, moreparticularly, to a semi-transmission type liquid crystal display whichreflects incident light coming from outside to provide a display lightsource and transmits light from a light source at the back.

2. Description of the Related Art

There is a reflection type liquid crystal display (LCD) known which hasa reflector inside and reflects incident external light by the reflectorto provide a display light source, thereby eliminating the need for abacklight as a light source and a transmission type liquid crystaldisplay equipped with a backlight as a light source.

As the reflection type liquid crystal display can be designed with lowerpower consumption, thinner and lighter than the transmission type liquidcrystal display, it is mainly used for a portable terminal. This isbecause as light input from outside is reflected at the reflector in thedisplay, the light can be used as a display light source, thuseliminating the need for a backlight. The transmission type liquidcrystal display has such a characteristic as having a better visibilitythan the reflection type liquid crystal display in case where ambientlight is dark.

As a reflector which improves the luminance of a reflection type liquidcrystal display, there is one which, for example, has isolatedprojections formed on the surface of the reflector leaving an organicinsulating film in a photolithography process, and an interlayer film isprovided on the projections, thereby yielding a smooth undulated shapewith mountain portions comprised of the projections and the other orvalley portions, so that an undulation pattern is formed on the surfaceof the reflector (see Japanese Patent No. 2825713).

FIG. 29 is a plan view showing an example of the undulation patternformed on the conventional reflector. shown in FIG. 29, the undulationpattern is formed by arranging a plurality of projections 2 with acircular planar shape as a projection pattern or a base pattern on thesurface of a reflector 1 in an isolated state. The undulation patterncauses irregular reflection of incident light, thus improving theluminance of the liquid crystal display.

The basic structure of the existing liquid crystal displays comprises aliquid crystal of an TN (Twisted Nematic) type, a single sheet polarizertype, an STN (Super Twisted Nematic) type, a GH (Guest-Host) type, aPDLC (Polymer Dispersed Liquid Crystal) type, a cholesteric type or thelike, a switching element which drives the liquid crystal and areflector or backlight provided inside or outside a liquid crystal cell.Those ordinary liquid crystal displays employ an active matrix drivesystem which can achieve high definition and high image quality usingthin film transistors (TFTS) or metal/insulating film/metal structurediodes (MIMs) as switching elements, and are equipped with a reflectoror backlight.

As a liquid crystal display which has advantages of both theconventional reflection type liquid crystal display and transmissiontype liquid crystal display, a semi-transmission type liquid crystaldisplay is disclosed (see Japanese Patent No. 2955277) which, as shownin FIG. 30, has gate interconnections 4 and source interconnections 5 soprovided as to run around pixel electrodes 3 of an active matrixsubstrate and intersect each other perpendicularly, has thin filmtransistors 6 provided on the pixel electrodes 3, has the gateinterconnections 4 and source interconnections 5 connected to the gateelectrodes and source electrodes of the thin film transistors 6 and hasreflection areas 7 of a metal film and transmission areas 8 of ITOformed in the pixel electrodes 3.

As the reflection areas and transmission areas are provided in the pixelelectrodes, the backlight can be turned off when the ambient light isbright so that the liquid crystal display can be used as a reflectiontype liquid crystal display, and thus demonstrates lower powerconsumption that is the characteristic of the reflection type liquidcrystal display. When the ambient light is dark, the backlight is turnedon so that the liquid crystal display is used as a transmission typeliquid crystal display, and thus demonstrates an improved visibility incase where ambient light is dark, which is the characteristic of thetransmission type liquid crystal display. Hereunder, a liquid crystaldisplay which can be used as a reflection type liquid crystal displayand as a transmission type liquid crystal display will be called as asemi-transmission type liquid crystal display.

In the liquid crystal display described in Japanese Patent No. 2955277,however, as shown in FIG. 31, undulations formed on an active matrixsubstrate are partly removed for planarization and transmission areas onthe pixel electrodes are formed on the flat portion of the active matrixsubstrate. The undulations formed on the active matrix substrate areprovided to efficiently reflect ambient light toward a user. In casewhere the areas of the undulations are reduced to form the transmissionareas so that the liquid crystal display is used as a reflection typeliquid crystal display with the backlight turned off, there arises aproblem that the luminance drops.

Japanese Patent Laid-Open No. 2001-75091 describes a reflector which hasisolated projections formed on the surface of the reflector by combiningthe above-described two prior arts, thereby forming an undulationpattern on the surface of the reflector, has openings formed in the topportions and bottom portions of the undulation pattern and uses openingsas transmission areas. Because the projections have isolated circularshapes, however, the reflector simultaneously reflects incident lightsfrom all the directions and has no directivity, the display luminance isundesirably reduced.

Because separation of the transmission areas from the reflection areasin the liquid crystal display described in Japanese Patent No. 2955277is simple, it is easy to form color filters with different thicknesseson the opposite substrate for different areas. As the reflectordescribed in Japanese Patent Laid-Open No. 2001-75091 has transmissionareas and reflection areas mixed in pixels, however, it is difficult toform color filters with different thicknesses on the opposite substratefor different areas. This makes it impossible to adjust the thicknessesof the color filters area by area. Accordingly, light passes the colorfilter formed on the opposite substrate twice in reflection mode butpasses it once in transmission mode. This changes the hue intransmission mode and reflection mode, so that the reduction inluminance and the change in hue lower the visibility.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide asemi-transmission type liquid crystal display which has an excellentvisibility in reflection mode as well as in transmission mode.

A liquid crystal display according to the present invention comprises:

a device substrate on which interconnections, thin film transistors andstorage capacitors are formed;

an opposite substrate so arranged as to face the device substrate;

a liquid crystal layer sandwiched between the device substrate and theopposite substrate;

a reflection electrode which is provided on the device substrate, whichhas an undulated shape and whose normal direction on a surface of thereflection electrode is distributed off-balanced to a specific azimuthangle and whose reflection light intensity depends on the azimuth angle;and

openings provided in a non-effective area of the reflection electrode.

As the openings are provided in the reflection electrode, light isirradiated by a backlight or the like from the opposite side of thedevice substrate to the liquid crystal layer in transmission mode,allowing the light to pass the liquid crystal layer for liquid crystaldisplay, so that display can be recognized even under a darkenvironment. As the normal direction of the reflection electrode isdistributed unevenly to a specific azimuth angle, the undulated shape onthe surface of the reflector is formed with anisotropy and thereflection light intensity depends on the azimuth angle, it is possibleto increase the reflection light intensity in the normal direction ofthe reflector which has a polar angle of 0 degree at a specific bearingangle. This increases the amount of light reflected to a viewer, therebyensuring an improvement of the visibility of the display that uses thereflector.

A liquid crystal display according to another aspect of the presentinvention comprises:

a device substrate on which interconnections, thin film transistors andstorage capacitors are formed;

an opposite substrate so arranged as to face the device substrate;

a liquid crystal layer sandwiched between the device substrate and theopposite substrate;

a first color filter formed on the opposite substrate;

a second color filter formed on the thin film transistors;

a reflection electrode formed on the second color filter and having anundulated shape; and

openings provided in a non-effective area of the reflection electrode.

As color filters are formed on the opposite substrate and the devicesubstrate, light passes the color filter on the opposite substrate sidetwice in reflection mode and passes the color filters on the devicesubstrate and the opposite substrate once each in transmission mode.This can make it possible to reduce a change in color in both modes. Itis also possible to respectively set the hues in transmission mode andreflection mode.

The liquid crystal display can be constructed in such a way that anormal direction on a surface of the reflection electrode is distributedunevenly to a specific azimuth angle and a polar angle distribution of areflection light intensity at the azimuth angle has two or more peakvalues.

Accordingly, the undulated shape on the surface of the reflector isformed with anisotropy, the reflection light intensity depends on theazimuth angle and two or more peak values appear in the polar angledistribution of the reflection light intensity at the azimuth angle.This makes it possible to increase the reflection light intensity in thenormal direction of the reflector which has a polar angle of 0 degree ata specific bearing angle.

The undulated shape can be designed in such a way as to have recesseswith a shape of a closed figure formed by a plurality of line-likeprojection patterns.

By forming the undulated shape by projection patterns and insulatinglayer and changing the line width, line length and thickness of theprojection patterns and the thickness of the insulating layer, it ispossible to design the undulated shape in such a way as to maximize theanisotropy of the reflector and the reflection light intensity in thenormal direction.

For example, the liquid crystal display is characterized in that theopenings are provided in the non-effective area of the reflectionelectrode as a transmission area, an effective area of the reflectionelectrode is a reflection area, and a potential difference between adrive voltage applied to that surface of the device substrate whichfaces the liquid crystal layer and a drive voltage applied to thatsurface of the opposite substrate which faces the liquid crystal layeris smaller in the transmission area than in the reflection area.

As the drive voltage applied to the liquid crystal layer in thereflection electrode is lower than the drive voltage applied to theliquid crystal layer in the transmission area, a change in thebirefringence of the liquid crystal layer in the reflection area becomessmaller than a change in the birefringence of the liquid crystal layerin the transmission area. This makes it possible to set the optimalchange in birefringence in each of the reflection mode and transmissionmode, so that the output light intensity can be optimized in both modes.

The liquid crystal display is characterized in that the non-effectivearea has, for example, a tilt angle of 0 degree to 2 degrees and/or atilt angle of 10 degrees or higher.

As the non-effective area where the openings are formed has a tilt angleof 0 degree to 2 degrees and/or a tilt angle of 10 degrees or higher,the non-effective area cannot efficiently reflect light input from theopposite substrate toward a viewer. Therefore, the luminance does notsignificantly drop even in reflection mode in which the light input fromthe opposite substrate is reflected at the reflection electrode forliquid crystal display.

For example, the liquid crystal display is characterized in that theopenings are provided only in that area of the reflection electrodewhich overlaps that area of the device substrate which passes light.

The number of openings that do not pass light is reduced by forming theopenings only in that area of the device substrate which passes light,thereby improving the light reflection efficiency.

The liquid crystal display can be constructed in such a way that theopenings are not provided only in that area of the reflection electrodewhich overlaps the interconnections, the thin film transistors and thestorage capacitors.

The interconnections, the thin film transistors and the storagecapacitors are formed of opaque materials. Even if openings are formedin those areas of the reflection electrode which overlaps theinterconnections, the thin film transistors and the storage capacitors,therefore, it is not possible to pass light from the backlight. Ifopenings are formed in the mentioned areas, the interconnections, thelights reflected by the thin film transistors and the storage capacitorschange the displayed colors of the liquid crystal. Therefore, forming noopenings in those areas can prevent the liquid crystal display colorsfrom changing.

The number of the openings in pixels can be set for each display color.

As the number of the openings in pixels can be made different displaycolor by display color, the color balance in the transmission modedisplay can be changed. In case where the best color balance inreflection mode differs from that in transmission mode, the colorbalances in reflection mode and transmission mode can be changed. Thiscan ensure liquid crystal display in such a way that the color balancebecomes optimal in both modes.

The areas of the openings in pixels can be set for each display color.

As the liquid crystal display is constructed in such a way that theareas of the openings in pixels differ display color by display color,the color balance in the transmission mode display can be changed. Incase where the best color balance in reflection mode differs from thatin transmission mode, the color balances in reflection mode andtransmission mode can be changed. This can ensure liquid crystal displayin such a way that the color balance becomes optimal in both modes.

The mode of a liquid crystal molecular alignment of the liquid crystallayer can be one of a homogeneous type, homeotropic type, a TN type, aHAN (Hybrid Aligned Nematic) type and an OCB (Optically CompensatedBend) type.

The luminance of the liquid crystal display in reflection mode andtransmission mode can be enhanced regardless of the mode of the liquidcrystal molecular alignment of the liquid crystal layer. It is thereforepossible to select the liquid crystal mode in accordance with the usageand the production cost.

The mode of a liquid crystal molecular alignment of the liquid crystallayer can be set in an area where the reflection electrode exists and anarea of the openings for each area.

The retardation of the liquid crystal layer in reflection mode andtransmission mode can be changed by setting the mode of the liquidcrystal molecular alignment in reflection mode can be made differentfrom the one in transmission mode. This makes it possible to enhance theoutput light intensity in both modes.

The liquid crystal display can be constructed in such a way that thetransparent electrode is formed on the device substrate and thereflection electrode is formed in contact with the transparent electrodeon that side of the liquid crystal layer.

As the reflection electrode is formed on the transparent electrode, thedirection of an electric field around each opening can be stabilized.This can suppress the disturbance of the liquid crystal molecularalignment.

A quarter-wave plate can be provided on a liquid crystal layer side ofthe opposite substrate.

The provision of the quarter-wave plate on the liquid crystal layer sideof the opposite substrate can prevent the quarter-wave plate from beingdeteriorated by external factors, such as the ultraviolet rays andhumidity, thereby leading to the elongated life of the liquid crystaldisplay. Because the quarter-wave plate itself is formed of a materialaligned that shows a liquid crystallinity, it is possible to eliminatethe need for coating of an alignment film and a rubbing process to alignthe liquid crystal layer. This can contribute to shortening themanufacturing time and reducing the production cost.

The liquid crystal display can be constructed in such a way that secondopenings are formed in that area of the quarter-wave plate which facesthe openings.

With the thickness of the liquid crystal layer optimized for thereflection mode, a higher output light intensity can be acquired in thetransmission mode that uses the quarter-wave plate than in thetransmission mode that does not use the quarter-wave plate. Forming thesecond openings in that area of the quarter-wave plate which faces theopenings can provide display without the quarter-wave plate intransmission mode, thus making it possible to increase the luminance intransmission mode.

A cholesteric liquid crystal can be provided on an opposite side of thedevice substrate to the liquid crystal layer.

Because the cholesteric liquid crystal shows the characteristic which isthe characteristics of a sheet polarizer and a quarter-wave platecombined together, the use of the cholesteric liquid crystal in place ofthe sheet polarizer and the quarter-wave plate can contribute toshortening the manufacturing time and reducing the production cost.

A second quarter-wave plate can be provided on a liquid crystal layerside of the device substrate.

The provision of the quarter-wave plate on the liquid crystal layer sideof the device substrate can prevent the quarter-wave plate from beingdeteriorated by external factors, such as the ultraviolet rays andhumidity, thereby leading to the elongated life of the liquid crystaldisplay. Because the quarter-wave plate itself is formed of a materialaligned that shows a liquid crystallinity, it is possible to eliminatethe need for coating of an alignment film and a rubbing process to alignthe liquid crystal layer. This can contribute to shortening themanufacturing time and reducing the production cost.

A cholesteric liquid crystal can be provided on an opposite side of thedevice substrate to the liquid crystal layer and a second quarter-waveplate can be provided between the cholesteric liquid crystal and thedevice substrate.

As the cholesteric liquid crystal and the quarter-wave plate areprovided on the opposite side of the device substrate to the liquidcrystal layer, it is possible to enhance the output light intensity ofthe liquid crystal display in reflection mode as well as in transmissionmode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a liquid crystal display accordingto a first embodiment;

FIGS. 2A through 2F are cross-sectional views illustrating, step bystep, a method of manufacturing the liquid crystal display shown in FIG.1;

FIGS. 3A and 3B are exemplary diagrams showing the relationship betweeninput light and reflected light;

FIG. 4 is a plan view of projection patterns on a reflector;

FIG. 5 is a cross-sectional view of the projection patterns;

FIG. 6 is a graph showing the distribution of tilt angle;

FIG. 7 is a plan view of a non-effective area pattern for formingopenings;

FIG. 8 is a diagram depicting the direction of an electric field aroundan opening;

FIG. 9 is a diagram showing the structure of one pixel of the liquidcrystal display;

FIG. 10 is a diagram showing the color balances in reflection mode andtransmission mode in color coordinates;

FIG. 11 is a cross-sectional view showing the reflector, a polar angleand an azimuth angle;

FIGS. 12A and 12B are diagrams showing an azimuth angle dependency ofthe output light intensity on an anisotropic reflector;

FIGS. 13A and 13B are diagrams showing an improvement on the reflectedlight intensity at the anisotropic reflector at an azimuth angle of 180degrees;

FIG. 14 is a cross-sectional view of a liquid crystal display accordingto a second embodiment;

FIGS. 15A through 15F are cross-sectional views illustrating, step bystep, a method of manufacturing the liquid crystal display shown in FIG.14;

FIG. 16 is a cross-sectional view of a liquid crystal display accordingto a third embodiment;

FIGS. 17A through 17F are cross-sectional views illustrating, step bystep, a method of manufacturing the liquid crystal display shown in FIG.16;

FIGS. 18A through 18E are diagrams showing the directions of alignmentof liquid crystal molecules in the modes of a liquid crystal layer;

FIGS. 19A to 19C are diagrams showing how to generate the liquid crystalmodes of a transmission section and a reflection section;

FIG. 20 is a diagram showing the layout of a quarter-wave plate and asheet polarizer in a TN type;

FIGS. 21A through 21I are diagrams showing possible layouts of thequarter-wave plate and the sheet polarizer;

FIG. 22 is a diagram depicting an embodiment in which the quarter-waveplate of the transmission section is removed;

FIG. 23 is a graph of the thickness of the liquid crystal layer 13 andthe output light intensity in transmission mode;

FIG. 24 is a diagram depicting an embodiment in which a cholestericliquid crystal is laid on a lower substrate;

FIG. 25 is a diagram depicting an embodiment in which a cholestericliquid crystal and a quarter-wave plate are laid on a lower substrate;

FIG. 26 is a cross-sectional view of a liquid crystal display accordingto a ninth embodiment;

FIG. 27 is an equivalent circuit diagram of the liquid crystal displayof the ninth embodiment;

FIGS. 28A through 28F are cross-sectional views illustrating, step bystep, a method of manufacturing the liquid crystal display shown in FIG.26;

FIG. 29 is a plan view showing an example of projection patterns formedon a conventional reflector;

FIG. 30 is a diagram showing pixels of a conventional semi-transmissiontype liquid crystal display; and

FIG. 31 is a cross-sectional view of the conventional semi-transmissiontype liquid crystal display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described below with reference tothe accompanying drawings. FIG. 1 is a partial cross-sectional view of asemi-transmission type liquid crystal display according to the firstembodiment of the present invention. As shown in FIG. 1, asemi-transmission type liquid crystal display 10 has, inside, a lowersubstrate 11, an opposite substrate 12 so arranged as to face the lowersubstrate 11 and a liquid crystal layer 13 sandwiched between the lowersubstrate 11 and the opposite substrate 12.

The semi-transmission type liquid crystal display 10 employs an activematrix system which has, for example, thin film transistors (TFTs)provided as switching elements pixel by pixel.

The lower substrate 11 has an insulative substrate 14, an insulatingprotection film 15, TFTs 16, an insulating layer 17, projection patterns18, a second insulating layer 19 and a reflection electrode 20. Theinsulating protection film 15 is deposited on the insulative substrate14 and the TFTs 16 are formed on the insulating protection film 15. EachTFT 16 has a gate electrode 16 a on the insulative substrate 14, a drainelectrode 16 b, a semiconductor layer 16 c and a source electrode 16 d,the last three electrodes lying on the insulating protection film 15covering the gate electrode 16 a.

The projection patterns 18 are formed on the insulating protection film15 and the TFT 16 via the first insulating layer 17 or the sourceelectrode 16 d of the TFT 16. The second insulating layer 19 isdeposited, covering the projection patterns 18, the first insulatinglayer 17 and the source electrode 16 d. A contact hole 21 reaching thesource electrode 16 d is bored in the second insulating layer 19.

Further, the reflection electrode 20 is deposited, covering the contacthole 21 and the second insulating layer 19. The reflection electrode 20is connected to the source electrode 16 d of the TFT 16 and has afunction as a reflector and a pixel electrode. The projection patterns18 and the second insulating layer 19 cause the reflection electrode 20to have an undulated surface. The reflection electrode 20 is removedfrom non-effective areas on the undulated surface of the reflectionelectrode 20 which are equivalent to the top portions and bottomportions, thereby forming openings 27 in the second insulating layer 19.The “non-effective area” mentioned here is an area on the undulatedsurface of the reflection electrode 20 where it is difficult toefficiently reflect external light toward a viewer.

A gate terminal portion 22 on the insulative substrate 14 and a drainterminal portion 23 on the insulating protection film 15 covering thegate terminal portion 22 are formed in a terminal area provided in theperipheral portion of the lower substrate 11.

The opposite substrate 12 has a transparent electrode 24, a color filter25 and an insulative substrate 26 laminated in order from that side ofthe liquid crystal layer 13. Incident light Li input to the oppositesubstrate 12 from the insulative substrate 26 travels from the oppositesubstrate 12 and reaches the lower substrate 11 through the liquidcrystal layer 13, and is reflected at the reflection electrode 20 tobecome reflected light Lr. The reflected light Lr travels through theliquid crystal layer 13 again and comes out of the opposite substrate 12from the transparent electrode 24.

FIGS. 2A through 2F are explanatory diagrams showing a reflectionelectrode fabricating process in the process of manufacturing thesemi-transmission type liquid crystal display shown in FIG. 1. As shownin FIG. 2A, first, the TFT 16 as a switching element is formed.

The gate electrode 16 a is formed on the insulative substrate 14 and theinsulating protection film 15 is deposited. Then, the drain electrode 16b, the semiconductor layer 16 c and the source electrode 16 d are formedon the insulating protection film 15. Further, the first insulatinglayer 17 is deposited, covering the TFT 16.

The switching element is not limited to the TFT 16 but a substrate forother switching elements, such as a diode, may be prepared as well.

Next, as shown in FIG. 2B, an organic resin is applied onto the firstinsulating layer 17, after which exposure and developing processes arecarried out to form a plurality of projection patterns 18 for formingthe undulation pattern on the surface of the reflection electrode 20using a projection pattern forming mask.

Then, as shown in FIG. 2C, the organic resin is baked. The baking makesthe corner portions of the organic resin round.

Next, an interlayer film of an organic resin is applied in such a way asto cover the projection patterns 18 to yield a smooth undulated shape.Then, exposure and developing processes are carried out to bore thecontact hole 21. Thereafter, the interlayer film is baked to form thesecond insulating layer 19 as shown in FIG. 2D.

Next, as shown in FIG. 2E, the reflection electrode 20 which is analuminum (Al) thin film covering the contact hole 21 and the secondinsulating layer 19 is formed in association with the forming positionof the reflection electrode 20.

Thereafter, as shown in FIG. 2F, with a mask corresponding to the topportions and bottom portions of the undulated surface of the reflectionelectrode 20, exposure and developing processes are carried out using aphotoresist to remove top portions and bottom portions of the reflectionelectrode 20, thereby forming the openings 27.

The material for the reflection electrode 20 is not limited to Al, butconductive materials, such as Ag, may be used as well. Because the shapeof the undulated surface of the reflection electrode 20 is determined bythe pattern of the projection patterns 18, the pattern of the mask thatis used at the time of forming the openings 27 is generated based on theprojection pattern forming mask used in FIG. 2B.

In the reflection electrode fabricating process, the organic interlayerfilm (undulated layer) between the Al film and the TFT substrate may beformed by a single layer instead of two layers. At the time of formingthe openings 27 in FIG. 2F, the second insulating layer 19 around theopenings 27 can be partially etched out so that light from a backlight28 can pass efficiently.

Next, an area where the openings 27 are formed will be discussed. FIG.3A exemplarily shows the light Li which is input to a reflector 1 wherethe openings 27 are not formed and the light Lr which is reflected atthe reflector 1 to be seen by a viewer. Let an incident angle Ti and areflection angle Tr be the angles formed by the incident light Li andthe reflected light Lr with respect to the normal direction of thereflector 1. As the incident angle Ti is reflected at the Al layerformed in an undulated pattern by the projection patterns 18 and theinsulating layer, the incident angle Ti and the reflection angle Tr takedifferent values.

FIG. 3B is a diagram exemplarily showing the reflection of lightincident to one point A on the Al layer having undulations. FIG. 3Bshows only the surface shape of the Al layer and the reflector 1 for thesake of simplicity. In case where the incident light Li is input to thepoint A on the undulations, the light is reflected at the point A on thecontact surface of the Al layer, so that the reflected light Lr isreflected with the normal direction at the point A as a symmetricalaxis. Given that the angle formed by the contact surface of the Al layerand the reflector 1 at the point A is defined as a tilt angle θ at thepoint A, the distribution of the incident light Li in the direction ofreflection depends on the distribution of the tilt angle θ of theundulations of the Al layer. Therefore, it is important to design thedistribution of the tilt angle θ in such a way that a viewer Psubjectively evaluates the luminance of the reflector 1 and recognizesthe reflection as bright reflection.

A description will now be given of the design of the undulation patternformed on the surface of the reflector 1 by the projection patterns 18and the second insulating layer 19. FIG. 4 two-dimensionally shows theprojection patterns formed on the reflector, and the hatched portion inthe diagram is an area where the projection patterns 18 are formed.Actually, a plurality of projection patterns are laid out with a certainroughness, yielding the layout of triangles. Although the example showsthe projection patterns forming the sides of a plurality of triangles,the undulation pattern may take any form as long as a plurality ofline-like projection patterns form a closed figure, such as a rectangleor an ellipsis.

FIG. 5 exemplarily shows a cross-sectional view of the projectionpatterns between two points in FIG. 4. Let L be the center distance ofthe projection patterns 18, W be the width of the projection patterns18, D be the height of the projection patterns 18, d be the height atwhich the height of the second insulating layer 19 becomes minimum andAD be a height difference between a point at which the height of thesecond insulating layer 19 becomes maximum and a point at which theheight of the second insulating layer 19 becomes minimum. A the Al film(reflection electrode 20) coated on the top surface of the secondinsulating layer 19 is very thin, its thickness is neglected and notshown.

The reflectors 1 were prepared by variously changing the values of theparameters of the projection patterns 18, L, W, D, d and ΔD, and wereused in a reflection type liquid crystal display plate with no openings27 formed therein, and a viewer made subjective evaluation on theluminance and interference. FIG. 6 shows the results of the evaluationon the distribution of the tilt angle for each of the reflectors whichhad good results on the subjective evaluation and those which had badresults. A graph A is the distribution of the tilt angle for the goodresults and the tilt angle ranging from 2 degrees to 10 degrees occupies50% or more. A graph B is the distribution of the tilt angle for thepoor results and the tilt angle of 0 degree occupies 15% or more.

By setting the parameters D, W, ΔD, d and L to control the distributionof the tilt angle, the luminance in the direction toward the viewer Pfor the reflection type liquid crystal display which has a directivityto the direction of light reflection can be improved.

The area of the reflection electrode 20 where the tilt angle θ lies in arange of 0 degree to 2 degrees reflects the light input from the normaldirection of the reflector 1 in the normal direction, so that it causessuch light reflection as to show the image of the viewer P. This areadoes not contribute much to an improvement of the luminance of theliquid crystal display. The area of the reflection electrode 20 wherethe tilt angle θ lies in a range of 10 degree or greater is not likelyto reflect external light toward the viewer P and does not contributemuch to an improvement of the luminance of the liquid crystal display.In the following description, the areas where the tilt angle θ is 0 to 2degrees and 10 degree or greater are called non-effective areas.

As the openings 27 are formed by removing the reflection electrode 20 atthe non-effective areas, the light from the backlight 28 is transmittedthrough the openings 27. In this case, the first insulating layer 17,the projection patterns 18 and the second insulating layer 19 are formedof transparent materials.

The areas where the tilt angle θ is 0 to 2 degrees are equivalent to thetop portions and bottom portions of the undulated surface and the areaswhere the tilt angle θ is equal to or greater than 10 degrees areequivalent to the polar changing portions of the undulations. Becausethe non-effective areas are determined by the parameters D, W, ΔD, d andL as shown in FIG. 5, therefore, a mask pattern corresponding to thenon-effective areas can be generated based on the pattern of theprojection pattern forming mask used in FIG. 2B.

If the projection patterns 18 are formed by using the projection patternforming mask as shown in FIG. 4, the non-effective areas become what isindicated by the hatched portion in FIG. 7. Therefore, a mask having theshape of the hatched portion in FIG. 7 is applied onto the reflector 1and the non-effective areas of the reflection electrode 20 are removedby photoresisting and etching, thus forming the openings 27. The removalof the reflection electrode 20 by etching is likely to increase theremoved area due to overetching progressed depending on the etchingconditions. In this respect, it is desirable that the mask with theshape of the hatched portion in FIG. 7 should be targeted for the areaswhere the tilt angle θ is 0 to 2 degrees and the areas where the tiltangle θ is equal to or greater than 10 degrees.

An electrode for generating an electric field on the liquid crystallayer 13 does not exist in the openings 27 so that the electric fieldaround the openings 27 of the liquid crystal layer 13 is disturbed.Because the size of the openings 27 is about several micrometers,however, the direction of the electric field, 29, around the openings 27is the direction in which an electric field generated effectively actsbetween the end portion of the reflection electrode 20 and thetransparent electrode 24 of the opposite substrate 12, as shown in FIG.8. The formation of the openings 27 in the non-effective areas does nottherefore significantly deteriorate the display characteristics of thesemi-transmission type liquid crystal display.

The planar distribution of the openings 27 will now be discussed. FIG. 9is a plan view exemplarily showing one pixel of the semi-transmissiontype liquid crystal display in enlargement, and shows that one pixel ofthe semi-transmission type liquid crystal display is comprised of thegate interconnections 4, drain interconnections 37, the TFT 16 and thestorage capacitor 30. The storage capacitor 30 is a capacitancecomponent formed by arranging the storage capacitor interconnection andthe drain electrode 16 b in such a way as to face each other via theinsulating protection film 15 and serves to suppress a variation involtage as it is inserted in parallel to the liquid crystal. The firstinsulating layer 17, the projection patterns 18, the second insulatinglayer 19 and the reflection electrode 20 are formed on the pixel areashown in FIG. 8. Although FIG. 9 illustrates a common storage typelayout, other layouts, such as a gate storage layer, can be employedwithout raising any problem.

Because the gate interconnections 4, the drain interconnections 37, theTFT 16 and the storage capacitor interconnection that constitutes thestorage capacitor 30 are generally not formed of transparent materials,the light from the backlight 28 cannot be transmitted. Even if theopenings 27 are formed in the areas where the reflection electrode 20overlaps the gate interconnections 4, the drain interconnections 37, theTFTs 16 and the storage capacitor 30, therefore, the amount oftransmitted light does not increase. Therefore, the mask pattern isproduced so as not to form the openings 27 in the areas that overlap thegate interconnections 4, the drain interconnections 37, the TFTs 16 andthe storage capacitor 30 and photoresisting and etching are carried outusing the mask pattern. It is to be noted that such is not essential incase where the storage capacitor 30 is formed of a transparent material,such as ITO.

In general, as a filter of red (R), green (G) or blue (B) is used in thecolor filter 25 of the opposite substrate 12, the liquid crystal displaymakes color display by expressing RGB. In the above-describedsemi-transmission type liquid crystal display, the intensity balance ofthe RGB colors is determined with the reflection mode, taken as areference, that turns off the backlight 28 and provides display withreflected light. When the area of the openings 27 formed in the pixelsis identical in the RGB colors, the intensity balance of the RGB colorsin the TM that turns on the backlight 28 and provides display withtransmitted light becomes similar to the intensity balance in reflectionmode.

However, the use environment differs in both modes; for example, thereflection mode is used when the ambient area is bright and thetransmission mode is used when the ambient area is dark. Therefore, thefatigue the viewer P feels at the time of viewing the liquid crystaldisplay can be reduced by setting the intensity of blue (B) so as to setthe color temperature of the transmission mode balance higher than thatof the reflection mode balance as shown in the color coordinates in FIG.10, rather than setting the same RGB intensity balance for both modes.

At the time the openings 27 are formed, therefore, for the reflectionelectrode 20 of the pixels where the blue (B) color filter 25 is laid,the area of one opening 27 is increased or the number of the openings 27in the pixels is increased to adjust the amount of to-be-transmittedlight from the backlight 28, thereby setting the color temperaturehigher. Likewise, the red (R) or green (G) intensity can also beadjusted in accordance with the use environment of the liquid crystaldisplay and the adjustment is substantially the same as that in the caseof enhancing blue (B).

The method which determines the reflection characteristics of thereflection type liquid crystal display and is becoming standard in theindustry is the method of inputting light at an angle of 30 degrees fromthe normal direction of the reflector and measuring the relationshipbetween the polar angle, defined by the incident light and the normaldirection of the reflector, and the reflection light intensity in casewhere the angle with the normal direction of the reflector as the centeris taken as the azimuth angle. From the viewpoint of improving thevisibility of the liquid crystal display in use, it is required todesign the reflector in such a way as to enhance the reflection lightintensity at a polar angle of 0 degree (normal direction) under theabove conditions.

Checking the relationship between the azimuth angle and the reflectionlight intensity after light is irradiated on the reflector on which theprojection patterns 18 having triangles as basic figures as shown inFIG. 7 are formed from the direction of a polar angle of 30 degrees itis seen that the reflection light intensity periodically changes asshown in FIGS. 12A and 12B. Hereinafter, the reflector that has suchprojection patterns as to change the reflection light intensityaccording to the azimuth angle is called an anisotropic reflector whilethe reflector that has projection patterns which do not change thereflection light intensity according to the azimuth angle is called anisotropic reflector. The reason why the anisotropic reflector increasesthe reflection light intensity in a specific direction is that thedistribution in the normal direction at the undulations of the surfaceof the reflector is not uniform.

Light was irradiated on the reflector on which the projection patterns18 having basic figures of triangles are formed from the direction of apolar angle of 30 degrees and an azimuth angle of 0 degree, and therelationship between the polar angle and the reflection light intensitywas measured at an azimuth angle of 90 degrees which was horizontal tothe light source and at an azimuth angle of 180 degrees to the lightsource and by using the spectrometer IMUC (LCD 7000) of OtsukaElectronics Co., Ltd. At this time, light was input from one top of oneof the basic triangles and one side of each triangle was arranged to behorizontal to the spectrometer. FIG. 13A shows the results of measuringin the direction of an azimuth angle of 180 degrees and FIG. 13B showsthe results of measuring in the direction of an azimuth angle of 90degrees. It is seen that the measuring results in the direction of anazimuth angle of 90 degrees becomes the distribution of the reflectionlight intensity with a peak at a polar angle of 30 degrees and themeasuring results in the direction of an azimuth angle of 180 degreesbecomes the distribution of the reflection light intensity with peaks inthe vicinity of a polar angle of 30 degrees and a polar angle of 5degrees. It is apparent that the reflection light intensity at a polarangle of 0 degree is greater at an azimuth angle 180 degrees than at anazimuth angle 90 degrees. The seems to be have occurred as theanisotropic reflection characteristic shown in FIG. 7 causes thereflection light intensity to have a peak value near a polar angle of 5degrees in the measurement at an azimuth angle 180 degrees.

Because the reflection light intensity depends on the azimuth angle dueto anisotropic projection patterns, as mentioned above, the polar angledependency of the reflection light intensity takes a plurality of peakvalues. It was confirmed that as the peaks appeared near a polar angleof 0 to 10 degrees, the reflection light intensity at a polar angle of 0degree would be improved.

FIG. 14 is a partial cross-sectional view of a semi-transmission typeliquid crystal display according to the second embodiment of theinvention. As shown in FIG. 14, a semi-transmission type liquid crystaldisplay 10 has, inside, a lower substrate 11, an opposite substrate 12so arranged as to face the lower substrate 11 and a liquid crystal layer13 sandwiched between the lower substrate 11 and the opposite substrate12.

The lower substrate 11 has an insulative substrate 14, an insulatingprotection film 15, TFTs 16, an insulating layer 17, projection patterns18, a second insulating layer 19, a reflection electrode 20 and atransparent electrode 31. The insulating protection film 15 is depositedon the insulative substrate 14 and the TFTs 16 are formed on theinsulating protection film 15. Each TFT 16 has a gate electrode 16 a onthe insulative substrate 14, a drain electrode 16 b, a semiconductorlayer 16 c and a source electrode 16 d, the last three electrodes lyingon the insulating protection film 15 covering the gate electrode 16 a.

The projection patterns 18 are formed on the insulating protection film15 and the TFT 16 via the first insulating layer 17 or the sourceelectrode 16 d of the TFT 16. The second insulating layer 19 isdeposited, covering the projection patterns 18, the first insulatinglayer 17 and the source electrode 16 d. A contact hole 21 reaching thesource electrode 16 d is bored in the second insulating layer 19.

Further, the transparent electrode 31 and the reflection electrode 20are deposited, covering the contact hole 21 and the second insulatinglayer 19. The reflection electrode 20 is connected to the sourceelectrode 16 d of the TFT 16 and has a function as a reflector and apixel electrode. The transparent electrode 31 is a transparent electricconductor, such as ITO, and is electrically connected to the reflectionelectrode 20 so that the transparent electrode 31 serves as a pixelelectrode. The projection patterns 18 and the second insulating layer 19cause the reflection electrode 20 to have an undulated surface. Thereflection electrode 20 is removed from non-effective areas on theundulated surface of the reflection electrode 20 which are equivalent tothe top portions and bottom portions, thereby forming openings 27 in thestorage capacitor 30. The “non-effective area” mentioned here is an areaon the undulated surface of the reflection electrode 20 where it isdifficult to efficiently reflect external light toward a viewer.

A gate terminal portion 22 on the insulative substrate 14 and a drainterminal portion 23 on the insulating rotection film 15 covering thegate terminal portion 22 are formed in a terminal area provided in theperipheral portion of the lower substrate 11.

The opposite substrate 12 has a transparent electrode 24, a color filter25 and an insulative substrate 26 laminated in order from that side ofthe liquid crystal layer 13. Incident light Li input to the oppositesubstrate 12 from the insulative substrate 26 travels from the oppositesubstrate 12 and reaches the lower substrate 11 through the liquidcrystal layer 13, and is reflected at the reflection electrode 20 tobecome reflected light Lr. The reflected light Lr travels through theliquid crystal layer 13 again and comes out of the opposite substrate 12from the transparent electrode 24.

FIGS. 15A through 15F are explanatory diagrams showing a reflectionelectrode fabricating process in the process of manufacturing thesemi-transmission type liquid crystal display shown in FIG. 14. As shownin FIG. 15A, first, the TFT 16 as a switching element is formed.

The gate electrode 16 a is formed on the insulative substrate 14 and theinsulating protection film 15 is deposited. Then, the drain electrode 16b, the semiconductor layer 16 c and the source electrode 16 d are formedon the insulating protection film 15. Further, the first insulatinglayer 17 is deposited, covering the TFT 16.

The switching element is not limited to the TFT 16 but a substrate forother switching elements, such as a diode, may be prepared as well.

Next, as shown in FIG. 15B, an organic resin is applied onto the firstinsulating layer 17, after which exposure and developing processes arecarried out to form a plurality of projection patterns 18 for formingthe undulation pattern on the surface of the reflection electrode 20using a projection pattern forming mask.

Then, as shown in FIG. 15C, the organic resin is baked. The baking makesthe corner portions of the organic resin round.

Next, an interlayer film of an organic resin is applied in such a way asto cover the projection patterns 18 to yield a smooth undulated shape.Then, exposure and developing processes are carried out to bore thecontact hole 21.

Thereafter, the interlayer film is baked to form the second insulatinglayer 19 as shown in FIG. 15D.

Next, as shown in FIG. 15E, the transparent electrode 31 of ITO isformed on the second insulating layer 19 in association with the formingposition of the reflection electrode 20, after which the reflectionelectrode 20 which is an aluminum (Al) thin film covering the contacthole 21 and the second insulating layer 19 is formed.

Thereafter, as shown in FIG. 15F, with a mask corresponding to the topportions and bottom portions of the undulated surface of the reflectionelectrode 20, exposure and developing processes are carried out using aphotoresist to remove top portions and bottom portions of the reflectionelectrode 20, thereby forming the openings 27 as per the firstembodiment.

Because the transparent electrode 31 having a function as a pixelelectrode is exposed through the openings 27, an electric field is notdisturbed even around the openings 27 of the liquid crystal layer 13 sothat the display characteristics of the semi-transmission type liquidcrystal display will not be deteriorated.

FIG. 16 is a partial cross-sectional view of a semi-transmission typeliquid crystal display according to another embodiment of the invention.As shown in FIG. 16, a semi-transmission type liquid crystal display 10has, inside, a lower substrate 11, an opposite substrate 12 so arrangedas to face the lower substrate 11 and a liquid crystal layer 13sandwiched between the lower substrate 11 and the opposite substrate 12.The semi-transmission type liquid crystal display 10 employs an activematrix system which has, for example, TFTs provided as switchingelements pixel by pixel.

The lower substrate 11 has an insulative substrate 14, an insulatingprotection film 15, TFTs 16, an insulating layer 17, projection patterns18, a second insulating layer 19, a reflection electrode 20 and a colorfilter 25. The insulating protection film 15 is deposited on theinsulative substrate 14 and the TFTs 16 are formed on the insulatingprotection film 15. Each TFT 16 has a gate electrode 16 a on theinsulative substrate 14, a drain electrode 16 b, a semiconductor layer16 c and a source electrode 16 d, the last three electrodes lying on theinsulating protection film 15 covering the gate electrode 16 a.

The color filter 25 is deposited on the insulating protection film 15and the TFT 16 via the first insulating layer 17 or the source electrode16 d of the TFT 16 and projection patterns 18 are formed on the colorfilter 25. The second insulating layer 19 is deposited, covering theprojection patterns 18, the first insulating layer 17, the sourceelectrode 16 d and the color filter 25. A contact hole 21 reaching thesource electrode 16 d is bored in the second insulating layer 19 and thecolor filter 25.

Further, the reflection electrode 20 is deposited covering the contacthole 21 and the second insulating layer 19. The reflection electrode 20is connected to the source electrode 16 d of the TFT 16 and has afunction as a reflector and a pixel electrode. The projection patterns18 and the second insulating layer 19 causes the reflection electrode 20to have an undulated surface. The reflection electrode 20 is removedfrom non-effective areas on the undulated surface of the reflectionelectrode 20 which are equivalent to the top portions and bottomportions, thereby forming openings 27 in the second insulating layer 19.The “non-effective area” mentioned here is an area on the undulatedsurface of the reflection electrode 20 where it is difficult toefficiently reflect external light toward a viewer. A gate terminalportion 22 on the insulative substrate 14 and a drain terminal portion23 on the insulating protection film 15 covering the gate terminalportion 22 are formed in a terminal area provided in the peripheralportion of the lower substrate 11.

The opposite substrate 12 has a transparent electrode 24, the colorfilter 25 and an insulative substrate 26 laminated in order from thatside of the liquid crystal layer 13. Incident light Li input to theopposite substrate 12 from the insulative substrate 26 travels from theopposite substrate 12 and reaches the lower substrate 11 through theliquid crystal layer 13, and is reflected at the reflection electrode 20to become reflected light Lr. The reflected light Lr travels through theliquid crystal layer 13 again and comes out of the opposite substrate 12from the transparent electrode 24.

FIGS. 17A through 17F are explanatory diagrams showing a step-by-stepreflection electrode fabricating process in the process of manufacturingthe semi-transmission type liquid crystal display shown in FIG. 16. Asshown in FIG. 17A, first, the TFT 16 as a switching element is formed.The gate electrode 16 a is formed on the insulative substrate 14 and theinsulating protection film 15 is deposited. Then, the drain electrode 16b, the semiconductor layer 16 c and the source electrode 16 d are formedon the insulating protection film 15. Further, the first insulatinglayer 17 is deposited, covering the TFT 16. Then, the color filter 25 isdeposited on the first insulating layer 17. The switching element is notlimited to the TFT 16 but a substrate for other switching elements, suchas a diode, may be prepared as well.

Next, as shown in FIG. 17B, an organic resin is applied onto the colorfilter 25, after which exposure and developing processes are carried outto form a plurality of projection patterns 18 for forming the undulationpattern on the surface of the reflection electrode 20 using a projectionpattern forming mask.

Then, as shown in FIG. 17C, the organic resin is baked. The baking makesthe corner portions of the organic resin round.

Next, an interlayer film of an organic resin is applied in such a way asto cover the projection patterns 18 to yield a smooth undulated shape.Then, exposure and developing processes are carried out to bore thecontact hole 21. Thereafter, the interlayer film is baked to form thesecond insulating layer 19 as shown in FIG. 17D.

Next, as shown in FIG. 17E, the reflection electrode 20 which is analuminum (Al) thin film covering the contact hole 21 and the secondinsulating layer 19 is formed in association with the forming positionof the reflection electrode 20.

Then, as shown in FIG. 17F, with a mask corresponding to the topportions and bottom portions of the undulated surface of the reflectionelectrode 20, exposure and developing processes are carried out using aphotoresist to remove top portions and bottom portions of the reflectionelectrode 20, thereby forming the openings 27. The material for thereflection electrode 20 is not limited to Al, but conductive materials,such as Ag, may be used as well. Because the shape of the undulatedsurface of the reflection electrode 20 is determined by the pattern ofthe projection patterns 18, the pattern of the mask that is used at thetime of forming the openings 27 is generated based on the projectionpattern forming mask used in FIG. 17B.

In the reflection electrode fabricating process, the organic interlayerfilm (undulated layer) between the Al film and the TFT substrate may beformed by a single layer instead of two layers. At the time of formingthe openings 27 in FIG. 17F, the second insulating layer 19 around theopenings 27 can be partially etched out so that light from a backlight28 can pass efficiently.

In the display of the reflection mode, input light from the oppositesubstrate 12 passes the color filter 25 provided on the oppositesubstrate 12 twice until it becomes output light, In the display of thetransmission mode, the light from the backlight 28 passes the colorfilter 25 provided on the lower substrate 11 and the color filter 25provided on the opposite substrate 12 until it becomes output light. Inreflection and transmission modes, the light passes the color filtertwice, so that the liquid crystal display of the third embodiment canmake the color expression identical in both modes. It is also possibleto determine the balance of colors displayed independently between thetransmission mode and reflection mode.

An ECB (Electrically Controlled Birefringence) type, homogeneous type,homeotropic type, TN type, HAN type, OCB type or the like is used forthe liquid crystal layers 13 according to the first embodiment and thesecond embodiment.

FIGS. 18A through 18E are exemplary diagrams showing the directions ofalignment of liquid crystal molecules in the liquid crystal modes. Thoseliquid crystal modes are generally acquired by controlling the alignmentdirection of the liquid crystal molecules and the pretilt angle bycoating an alignment film on the lower substrate 11 after forming apattern of layers on the lower substrate 11 and rubbing the alignmentfilm in one direction with a cloth or the like or selecting the type ofthe alignment film.

In case where light reflection by the reflection electrode 20 and lighttransmission through the openings 27 are used together as in theinvention, the light travels in the liquid crystal layer 13 by adistance twice the thickness d of the liquid crystal layer 13 in thereflection section (an area of the reflection electrode 20) as the inputlight is reflected at the reflector and becomes output light while thelight travels in the liquid crystal layer 13 by a distance equal to thethickness d of the liquid crystal layer 13 in the transmission section(an area where the openings 27 are formed) until the input light becomesoutput light. The difference in light path between the reflectionsection and the transmission section produces a difference inretardation between the reflection mode and the transmission mode. Asthe alignment direction of the liquid crystal molecules differs, therefractive index differs in the aforementioned liquid crystal modes. Thedifference in retardation between the reflection mode and thetransmission mode is canceled out by making the alignment directions ofthe liquid crystal molecules in the reflection electrode 20 and theopenings 27 different from each other using the phenomenon.

FIGS. 19A to 19C are diagrams exemplarily showing a method ofmanufacturing a liquid crystal display, which makes the alignmentdirection of the liquid crystal molecules in the reflection electrode 20different from the alignment direction of the liquid crystal moleculesin the openings 27. As shown in FIG. 19A, polyimide alignment film 32which provides a pretilt angle of nearly 90 degrees is simultaneouslyapplied to the reflection electrode 20 and the openings 27 of the lowersubstrate 11, is heated and dried and ultraviolet rays are irradiatedfrom the lower substrate 11. Because of the presence of the reflectionelectrode 20, the ultraviolet rays are irradiated only on the polyimidealignment film 32 above the openings 27. The irradiation of theultraviolet rays decomposes the long-chain alkyl group of the polyimidealignment film 32 so that the portion of the liquid crystal which showsthe pretilt angle disappears, thus making the pretilt angle over theopenings 27 smaller. With regard to the alignment film which changes thepretilt angle by the irradiation of ultraviolet rays, the effect is thesame even if ultraviolet rays are irradiated after rubbing, so thatrubbing may be carried out prior to the irradiation of ultraviolet rays.

As shown in FIG. 19B, after the irradiation of ultraviolet rays, rubbingis performed in the direction where the liquid crystal should bealigned. Ultraviolet rays are not irradiated onto the polyimidealignment film 32 on the reflection electrode 20 so that thepretilt-angle predetermined angle stays close to 90 degrees. As rubbingdoes not significantly change the pretilt angle, alignment is vertical.As the irradiation of ultraviolet rays makes the pretilt angle smalleron the polyimide alignment film 32 above the openings 27, rubbing setshorizontal alignment.

As shown in FIG. 19C, as the opposite substrate 12 is processed with thealignment film that provides horizontal alignment and the alignment ismade horizontal by rubbing, the portion of horizontal alignment becomeshomogeneous alignment or TN alignment whereas the portion of verticalalignment becomes HAN alignment.

As the liquid crystal mode at the reflection electrode 20 and theopenings 27 is changed by using the method shown in FIGS. 19A–19C, thevalue of the retardation (Δn·d) is changed by using the difference inrefractive index brought about by the liquid crystal mode, so thatextreme brightness can be obtained in both the reflection mode andtransmission mode even with the same cell thickness.

In case where the mode of the liquid crystal layer 13 is the TN mode inthe semi-transmission type liquid crystal displays of the firstembodiment and the second embodiment, a sheet polarizer and aquarter-wave plate are arranged on the lower substrate 11 and theopposite substrate 12. FIG. 20 shows a cross-sectional view of a liquidcrystal display according to the fifth embodiment of the invention.

A sheet polarizer 33 is arranged between the insulative substrate 14 ofthe lower substrate and the backlight 28, and a quarter-wave plate 34 isarranged between the insulative substrate 14 and the second insulatinglayer 19. Another quarter-wave plate 34 is arranged on the liquidcrystal layer side surface of the insulative substrate 26 of theopposite substrate and another sheet polarizer 33 is arranged on theopposite side surface of the insulative substrate 26 to the liquidcrystal layer 13. The directions of polarization of the sheet polarizer33 on the lower substrate and the sheet polarizer 33 on the oppositesubstrate are so set as to be perpendicular to each other. Although notillustrated, the TFT 16, the insulating protection film 15, the gateterminal portion 22 and the drain terminal portion 23 are formed on thequarter-wave plate 34 on the lower substrate and the transparentelectrode 24 and the color filter 25 are formed between the quarter-waveplate 34 on the opposite substrate and the liquid crystal layer 13, asdone in FIGS. 1 and 2.

At the time of twisted alignment in reflection mode, light input fromoutside the opposite substrate passes through the sheet polarizer 33 tobecome linearly polarized light, which in turn passes the quarter-waveplate 34 to become right-handed circularly polarized light. The inputlight of right-handed circularly polarization passes the liquid crystallayer 13 in the twisted alignment to become linearly polarized light,and the reflected light of linearly polarization passes the liquidcrystal layer 13 in the twisted alignment to become right-handedcircularly polarized light. The reflected light which is right-handedcircularly polarized light passes the quarter-wave plate 34 to belinearly polarized light which in turn becomes output light.

At the time of vertical alignment in reflection mode, light input fromoutside the opposite substrate passes through the sheet polarizer 33 tobecome linearly polarized light, which in turn passes the quarter-waveplate 34 to become right-handed circularly polarized light. The inputlight of right-handed circularly polarization passes the liquid crystallayer 13 in the vertical alignment to become linearly polarized light,and is reflected at the reflection electrode 20 to become reflectedlight of left-handed circularly polarized light which is the reverserotary to the right-handed circularly polarized light. The reflectedlight of left-handed circularly polarization passes the liquid crystallayer 13 in the vertical alignment and passes the quarter-wave plate 34to be linearly polarized light. As the direction of polarization of thislinearly polarized light differs from the direction of polarization ofthe sheet polarizer 33, the reflected light does not pass the sheetpolarizer 33.

At the time of twisted alignment in transmission mode, light input fromthe backlight 28 passes through the sheet polarizer 33 to becomelinearly polarized light, which in turn passes the quarter-wave plate 34to become left-handed circularly polarized light. The input light ofleft-handed circularly polarization passes the liquid crystal layer 13in the twisted alignment to become transmitted light of right-handedcircularly polarization which is the reverse rotary to the left-handedcircularly polarized light. The transmitted light of right-handedcircularly polarization passes the quarter-wave plate 34 to becomelinearly polarized light which in turn becomes output light.

At the time of vertical alignment in transmission mode, light input fromthe backlight 28 passes through the sheet polarizer 33 to becomelinearly polarized light, which in turn passes the quarter-wave plate 34to become left-handed circularly polarized light. The input light ofleft-handed circularly polarization passes the liquid crystal layer 13in the vertical alignment and passes the quarter-wave plate 34 of theopposite substrate to become linearly polarized light. As the directionof polarization of the linearly polarized light differs from thedirection of polarization of the sheet polarizer 33, the transmittedlight does not pass the sheet polarizer 33.

Because the quarter-wave plates 34 are arranged closer to the liquidcrystal layer 13 than the drive motor 14 and the insulative substrate 26as shown in FIG. 20, the liquid crystal display once fabricated is notinfluenced by ultraviolet rays and humidity, which is an advantageous inview of the weather durability. That is, ultraviolet rays are absorbedby not only the sheet polarizer 33 but also the insulative substratewhich is a thick glass or plastic substrate, so that the ultravioletrays hardly reach the quarter-wave plate 34. It is therefore possible tosignificantly prevent the ultraviolet-rays dependent deterioration ascompared with the case where the quarter-wave plate 34 is arranged onthe opposite side of the liquid crystal layer 13. Further, the liquidcrystal display is not influenced by the humidity.

An adhesive which adheres the sheet polarizer to the quarter-wave platesuffers a possible humidity-oriented separation. The arrangement of thequarter-wave plate 34 on the liquid crystal layer side eliminates theneed for an adhesive between the sheet polarizer 33 and the quarter-waveplate 34, thereby solving the problem. This widens the range ofmaterials selectable for the quarter-wave plate 34 and makes it easierto improve the other performances, such as the transmittance.

Because the quarter-wave plate 34 itself is formed by aligning thematerial that shows liquid crystallinity, there is an effect of aligningthe liquid crystal material. Therefore, arranging the quarter-wave plate34 closer to the liquid crystal layer 13 than the transparent electrode24 and the reflection electrode 20 eliminates the need for applicationof an alignment film and a rubbing process. With a 90-degree twistedstructure, particularly, it is unnecessary to perform an alignmentprocess on the lower substrate and the opposite substrate. Further, therubbing process to align the liquid crystal is unnecessary even in theHAN type.

The sheet polarizer 33 can be arranged on the liquid crystal layer side.Because the insulative substrate has a thickness of about 0.7 mm, thereis a possibility that output light comes out from the adjoining pixelsvia the insulative substrate. The arrangement of the sheet polarizer 33on the liquid crystal layer side prevents the light from a pixel in anon-display state from reaching the insulative substrate. This reducesthe possibility of viewing light from the adjoining pixels and improvesthe visibility. FIGS. 21A through 21I show combinations of the layoutrelations of the quarter-wave plate, the sheet polarizer and theinsulative substrate. The diagrams illustrate only the positionalrelationships with the insulative substrate and do not show the otherstructural elements of the liquid crystal display.

In case where the mode of the liquid crystal layer 13 is the TN mode inthe semi-transmission type liquid crystal displays of the firstembodiment and the second embodiment, a sheet polarizer and aquarter-wave plate are arranged on the opposite substrate 12 and a sheetpolarizer is arranged on the lower substrate 11. A quarter-wave plate isomitted in an area corresponding to the transmission section of theopposite substrate. FIG. 22 shows a cross-sectional view of a liquidcrystal display according to the sixth embodiment of the invention.

A sheet polarizer 33 is arranged between the insulative substrate 14 ofthe lower substrate and the backlight 28. A quarter-wave plate 34 isarranged on the liquid crystal layer side surface of the insulativesubstrate 26 of the opposite substrate and another sheet polarizer 33 isarranged on the opposite side surface of the insulative substrate 26 tothe liquid crystal layer 13. The directions of polarization of the sheetpolarizer 33 on the lower substrate and the sheet polarizer 33 on theopposite substrate are so set as to be perpendicular to each other.Although not illustrated, the TFT 16, the insulating protection film 15,the gate terminal portion 22 and the drain terminal portion 23 areformed on the quarter-wave plate 34 on the lower substrate and thetransparent electrode 24 and the color filter 25 are formed between thequarter-wave plate 34 on the opposite substrate and the liquid crystallayer 13, as done in FIGS. 1 and 2.

Those areas of the quarter-wave plate 34 arranged on the oppositesubstrate which correspond to the openings 27 are removed by aphotoresisting process and etching process using the mask that has beenused at the time of forming the openings 27 in the reflection electrode20.

The intensity, Iλ, of output light in the case where light from thebacklight passes the sheet polarizer and quarter-wave plate of the lowersubstrate, passes the liquid crystal layer and passes the quarter-waveplate and sheet polarizer of the opposite substrate is given by:Iλ=½{Γ/2)(1/X·sin X)}2where λ is the wavelength of light, Δn·d is the retardation of theliquid crystal layer and Γ=2πΔn·d/λ and X={φ2+(Γ/2)2}½ on the assumptionthat the liquid crystal molecules are twisted evenly at a twist angle φ.

On the other hand, the intensity, Ip, of output light in the case wherelight from the backlight does not pass the quarter-wave plate but passesthe sheet polarizer of the lower substrate, passes the liquid crystallayer and passes the sheet polarizer of the opposite substrate is givenby:Ip=(½)(1/X·sin X)2[φ2·cos 2φ+sin 2φ(Γ/2) 2]+sin 2φ cos 2X−φ sin 2φ cosX(1/X·sin X).

FIG. 23 is a graph showing the results of computing the intensity Iλ ofthe output light that has passed the quarter-wave plate in transmissionmode and the intensity Ip of the output light that has not passed thequarter-wave plate based on the thickness of the liquid crystal layer.The birefringence (Δnd) at which the intensity of the output light inreflection mode becomes maximum is 270 nm. With the refractive index ofthe liquid crystal being 0.09, the thickness of the liquid crystal layerin reflection mode becomes about 3 μm. When the liquid crystal displayis designed with the reflection mode as a reference, the thickness ofthe liquid crystal layer becomes about 3 μm. It is therefore apparentthat in transmission mode the intensity Ip of the output light thatpasses only the sheet polarizer becomes greater than the intensity Iλ ofthe output light in the case where the quarter-wave plate is present.

As shown in FIG. 22, therefore, the intensity of the output light fromthe liquid crystal display can be increased in both the reflection modeand transmission mode by arranging no quarter-wave plate on the lowersubstrate and removing that area of the quarter-wave plate arranged onthe opposite substrate which faces the transmission section.

FIG. 24 is a diagram depicting another embodiment of the invention inwhich a cholesteric liquid crystal is laid on the opposite side of thelower substrate to the liquid crystal layer. The cholesteric liquidcrystal is the liquid crystal that has a molecular alignment having aspiral periodic structure. In case where the cholesteric liquid crystalhas a molecular alignment with a spiral period=P, of light incidentparallel to the spiral axis, only light having a wavelength width Δλ=PΔn(Δn=anisotropy of refractive index) around a wavelength λ=nP (where n isa mean refractive index of the liquid crystal) is selectively reflectedand the light of that wavelength range passes. In case of a leftwardcholesteric liquid crystal, light that satisfies the wavelengthcondition is separated into right-handed circularly polarized light andleft-handed circularly polarized light, and only the former polarizedlight is reflected and the latter passes directly. In case of arightward cholesteric liquid crystal, the opposite is applied.

A cholesteric liquid crystal 35 is arranged between the insulativesubstrate 14 of the lower substrate and the backlight. The quarter-waveplate 34 is arranged on the liquid crystal layer side of the insulativesubstrate 26 of the opposite substrate and the sheet polarizer 33 isarranged on the opposite side of the insulative substrate 26 to theliquid crystal layer 13. Although not illustrated, the TFT 16, theinsulating protection film 15, the gate terminal portion 22 and thedrain terminal portion 23 are formed on the lower substrate and thetransparent electrode 24 and the color filter 25 are formed between thequarter-wave plate 34 on the opposite substrate and the liquid crystallayer 13, as done in FIGS. 1 and 2. The cholesteric liquid crystal 35 iscomprised of three layers which have spiral periods corresponding to thewavelengths of RGB colors and which reflect the circularly polarizedlight of the same direction.

In the fifth embodiment, the same advantages as those of the fourthembodiment can be obtained by arranging the cholesteric liquid crystal35 instead of arranging the sheet polarizer 33 and the quarter-waveplate 34 on the lower substrate.

FIG. 25 is a diagram depicting another embodiment of the invention inwhich a quarter-wave plate and a cholesteric liquid crystal are arrangedon the opposite side of the lower substrate to the liquid crystal layerand a sheet polarizer and a quarter-wave plate are arranged on theopposite substrate. Those areas of the quarter-wave plate on theopposite substrate which face the openings 27 in the reflectionelectrode 20 are removed.

A cholesteric liquid crystal 35 is arranged between the insulativesubstrate 14 of the lower substrate and the backlight. A quarter-waveplate 34 is arranged between the backlight 28 and the cholesteric liquidcrystal 35. The quarter-wave plate 34 is arranged on the liquid crystallayer side of the insulative substrate 26 of the opposite substrate andthe sheet polarizer 33 is arranged on the opposite side of theinsulative substrate 26 to the liquid crystal layer 13. Although notillustrated, the TFT 16, the insulating protection film 15, the gateterminal portion 22 and the drain terminal portion 23 are formed on thequarter-wave plate 34 of the lower substrate and the transparentelectrode 24 and the color filter 25 are formed between the quarter-waveplate 34 on the opposite substrate and the liquid crystal layer 13, asdone in FIGS. 1 and 2.

Those areas of the quarter-wave plate 34 arranged on the oppositesubstrate which correspond to the openings 27 are removed by aphotoresisting process and etching process using the mask that has beenused at the time of forming the openings 27 in the reflection electrode20.

Arranging the cholesteric liquid crystal 35 and the quarter-wave plate34 instead of arranging the sheet polarizer 33 on the lower substratecan increase the output light intensity of the liquid crystal display inboth the reflection mode and transmission mode as per the fifthembodiment.

A further embodiment of the invention will be discussed below. FIG. 26is a cross-sectional view showing a part of the lower substrate of theninth embodiment in a simplified form. A contact hole 21 reaching thesource electrode 16 d of the TFT 16 is bored in the insulating layer 17.A transparent electrode 31, an insulating film 36 and a reflectionelectrode 20 are deposited, covering the contact hole 21 and theinsulating layer 17. The transparent electrode 31 is connected to thesource electrode 16 d or the drain electrode 16 b of the TFT 16 and hasa function to serve as a pixel electrode. The transparent insulatingfilm 36 of SiO₂ or the like is deposited between the transparentelectrode 31 and the reflection electrode 20. The reflection electrode20 is electrically connected to the transparent electrode 31 via theinsulating film 36, and has a function to serve as a reflector and apixel electrode.

The insulating layer 17 has an undulated surface, and the transparentelectrode 31 and the reflection electrode 20 formed on the insulatinglayer 17 have undulated surfaces too. The reflection electrode 20 andthe insulating film 36 are removed at the top areas and bottom areas ofthe undulated surface of the reflection electrode 20 and the openings 27are formed in such a way that the transparent electrode 31 contact theliquid crystal layer 13.

Although not illustrated, an alignment film of polyimide or the likewhich aligns the liquid crystal molecules is deposited, covering thereflection electrode 20 and transparent electrode 31. As the alignmentfilm is rubbed, the alignment direction of the liquid crystal moleculesof the liquid crystal layer 13 is determined. As the transparentelectrode 31 is electrically connected to the source electrode 16 d ofthe TFT 16 via the contact hole 21, the potential supplied by the TFT 16becomes equal to the potential of the transparent electrode 31. As thereflection electrode 20 is connected via the insulating film 36 to thetransparent electrode 31, however, the potential of the reflectionelectrode 20 becomes lower than the potential of the transparentelectrode 31. At this time, a capacitor is formed by the reflectionelectrode 20, the transparent electrode 31 and the insulating film 36.

An equivalent circuit of the liquid crystal display according to theninth embodiment becomes the one shown in FIG. 27. Provided that thestructure of sandwiching the liquid crystal layer 13 between the lowersubstrate 11 and the opposite substrate 12 is regarded as a capacitor,let CLC1 be the combination of the transparent electrode 31 in theopenings 27 and the opposite substrate 12, let CLC2 be the combinationof the reflection electrode 20 and the opposite substrate 12, and let Clbe the reflection electrode 20 connected to the transparent electrode 31via the insulating film 36. Because two capacitors, CLC2 and Cl, areconnected in series in the area of the reflection electrode 20, thevoltage applied by the TFT 16 is capacitively divided so that thevoltage applied to the liquid crystal layer 13 becomes lower than thevoltage applied only to the CLC1 in the area of the transparentelectrode 31.

It is known that with λ being the wavelength of light used for display,the reflection type liquid crystal display provides output light withthe highest intensity when the birefringence (retardation) of the liquidcrystal layer 13 is λ/4 while the transmission type liquid crystaldisplay provides output light with the highest intensity when thebirefringence is λ/2. It is also known that as the voltage applied tothe liquid crystal layer 13 is increased, the birefringence of theliquid crystal layer 13 is increased monotonously. It is thereforepossible to optimize the birefringence of the liquid crystal layer 13 inboth the transmission mode and reflection mode by depositing theinsulating film 36 on the transparent electrode 31 so as to provide theequivalent circuit shown in FIG. 27, which produces a potentialdifference between the surface of the transparent electrode 31 and thereflection electrode 20. Available materials for the insulating film 21are organic materials, such as SiN, SiO₂, acryl and arton. Because thecapacitances of the CLC1 ad CLC2 in FIG. 27 change according to thematerial for, and the thickness of, the liquid crystal layer 13 and therelationship between the applied voltage and the birefringence alsovaries depending on the material for the liquid crystal layer 13,however, it is necessary to adequately adjust the material for and thethickness of the insulating film 36.

FIGS. 28A through 28F are cross-sectional views showing a fabricationprocess for the lower substrate in the process of manufacturing thesemi-transmission type liquid crystal display shown in FIG. 26. First,as shown in FIG. 28A, the gate electrode 16 a is formed on theinsulative substrate 14, the insulating protection film 15 is depositedon the gate electrode 16 a and the drain electrode 16 b, thesemiconductor layer 16 c and the source electrode 16 d are formed on theinsulating protection film 15, thereby forming the substrate of the TFT16 as a switching element. The switching element is not limited to theTFT 16 but a substrate for other switching elements, such as a diode,may be prepared as well.

Further, the insulating layer 17 is deposited covering the TFT 16. Toform the undulated surface on the insulating layer 17, after thedeposition of the flat insulating layer 17, masking is applied and stepsare formed on the insulating layer 17 using a photoresist. Then, anannealing treatment is performed to make the corners of the steps of theinsulating layer 17 round, so that the insulating layer 17 formed hasgentle undulations on the surface.

Next, as shown in FIG. 28B, the contact hole 21 reaching the sourceelectrode 16 d is formed in the insulating layer 17. Then, as shown inFIG. 28C, the transparent electrode 31 of ITO is deposited, covering theinsulating layer 17 by sputtering, allowing the source electrode 16 d toelectrically contact the transparent electrode 31 via the contact hole21. Further, as shown in FIG. 28D, the insulating film 36 of SiO₂ isdeposited on the transparent electrode 31 by CVD. Then, the reflectionelectrode 20 which is an Al film is formed on the insulating film 36 byvacuum deposition, as shown in FIG. 28E.

Based on the mask that has been used in the process in FIG. 28B to formthe undulations on the insulating layer 17, the top areas and bottomareas of the undulated surface of the reflection electrode 20 arespecified. Using the mask that has holes opened at the positionscorresponding to the top areas and bottom areas, the reflectionelectrode 20 and the insulating film 36 at the top areas and bottomareas are removed by etching and a photoresist, thereby forming theopenings 27. As shown in FIG. 28F, the transparent electrode 31 isexposed at the openings 27.

The material for the reflection electrode 20 is not limited to Al, butother conductive materials can be used as well. The lower substrate 11is fabricated in the above-described manner and is made to face, via aframe member, the opposite substrate 12 on which the color filter andthe transparent electrode are deposited, and the liquid crystal layer 13is injected between both substrates, which completes the fabrication ofthe liquid crystal display.

According to the invention, as the openings are provided in thereflection electrode, light is irradiated by a backlight or the likefrom the opposite side of the device substrate to the liquid crystallayer in transmission mode, allowing the light to pass the liquidcrystal layer for liquid crystal display, so that display can berecognized even under a dark environment. As the normal direction of thereflection electrode is distributed unevenly to a specific azimuthangle, the undulated shape on the surface of the reflector is formedwith anisotropy and the reflection light intensity depends on theazimuth angle, it is possible to increase the reflection light intensityin the normal direction of the reflector which has a polar angle of 0degree at a specific bearing angle. This increases the amount of lightreflected to a viewer, thereby ensuring an improvement of the visibilityof the display that uses the reflector.

As color filters are formed on the opposite substrate and the devicesubstrate, light passes the color filter on the opposite substrate sidetwice in reflection mode and passes the color filters on the devicesubstrate and the opposite substrate once each in transmission mode.This can make it possible to reduce a change in color in both modes. Itis also possible to respectively set the hues in transmission mode andreflection mode. Further, the reflection electrode is formed on thecolor filters, the planarization of that surface of the device substratewhich contacts the liquid crystal layer becomes improved, making itpossible to effectively control the alignment direction in a rubbingprocess.

The undulated shape on the surface of the reflector is formed withanisotropy, the reflection light intensity depends on the azimuth angleand two or more peak values appear in the polar angle distribution ofthe reflection light intensity at the azimuth angle. This makes itpossible to increase the reflection light intensity in the normaldirection of the reflector which has a polar angle of 0 degree at aspecific bearing angle.

By forming the undulated shape by projection patterns and insulatinglayer and changing the line width, line length and thickness of theprojection patterns and the thickness of the insulating layer, it ispossible to design the undulated shape in such a way as to maximize theanisotropy of the reflector and the reflection light intensity in thenormal direction.

As the drive voltage applied to the liquid crystal layer in thereflection electrode is lower than the drive voltage applied to theliquid crystal layer in the transmission area, a change in thebirefringence of the liquid crystal layer in the reflection area becomessmaller than a change in the birefringence of the liquid crystal layerin the transmission area. This makes it possible to set the optimalchange in birefringence in each of the reflection mode and transmissionmode, so that the output light intensity can be optimized in both modes.

As the non-effective area where the openings are formed has a tilt angleof 0 degree to 2 degrees and/or a tilt angle of 10 degrees or higher,the non-effective area cannot efficiently reflect light input from theopposite substrate toward a viewer. Therefore, the luminance does notsignificantly drop even in reflection mode in which the light input fromthe opposite substrate is reflected at the reflection electrode forliquid crystal display.

The interconnections, the thin film transistors and the storagecapacitors are formed of opaque materials. Even if openings are formedin those areas of the reflection electrode which overlap theinterconnections, the thin film transistors and the storage capacitors,therefore, it is not possible to pass light from the backlight. Ifopenings are formed in the mentioned areas, the interconnections, thelights reflected by the thin film transistors and the storage capacitorschange the displayed colors of the liquid crystal. Therefore, forming noopenings in those areas can prevent the liquid crystal display colorsfrom changing.

As the number of the openings in pixels can be made different displaycolor by display color, the color balance in the transmission modedisplay can be changed. In case where the best color balance inreflection mode differs from that in transmission mode, the colorbalances in reflection mode and transmission mode can be changed. Thiscan ensure liquid crystal display in such a way that the color balancebecomes optimal in both modes.

The luminance of the liquid crystal display in reflection mode andtransmission mode can be enhanced regardless of the mode of the liquidcrystal molecular alignment of the liquid crystal layer. It is thereforepossible to select the liquid crystal mode in accordance with the usageand the production cost.

The retardation of the liquid crystal layer in reflection mode andtransmission mode can be changed by setting the mode of the liquidcrystal molecular alignment in reflection mode can be made differentfrom the one in transmission mode. This makes it possible to enhance theoutput light intensity in both modes.

As the reflection electrode is formed on the transparent electrode, thedirection of an electric field around each opening can be stabilized.This can suppress the disturbance of the liquid crystal molecularalignment.

The provision of the quarter-wave plate on the liquid crystal layer sideof the opposite substrate can prevent the quarter-wave plate from beingdeteriorated by external factors, such as the ultraviolet rays andhumidity, thereby leading to the elongated life of the liquid crystaldisplay. Because the quarter-wave plate itself is formed of a materialaligned that shows a liquid crystallinity, it is possible to eliminatethe need for coating of an alignment film and a rubbing process to alignthe liquid crystal layer. This can contribute to shortening themanufacturing time and reducing the production cost.

With the thickness of the liquid crystal layer optimized for thereflection mode, a higher output light intensity can be acquired in thetransmission mode that uses the quarter-wave plate than in thetransmission mode that does not use the quarter-wave plate. Forming thesecond openings in that area of the quarter-wave plate which faces theopenings can provide display without the quarter-wave plate intransmission mode, thus making it possible to increase the luminance intransmission mode.

Because the cholesteric liquid crystal shows the characteristic which isthe characteristics of a sheet polarizer and a quarter-wave platecombined together, the use of the cholesteric liquid crystal in place ofthe sheet polarizer and the quarter-wave plate can contribute toshortening the manufacturing time and reducing the production cost.

As the cholesteric liquid crystal and the quarter-wave plate areprovided on the opposite side of the device substrate to the liquidcrystal layer, it is possible to enhance the output light intensity ofthe liquid crystal display in reflection mode as well as in transmissionmode.

1. A liquid crystal display comprising: a device substrate on whichinterconnections, thin film transistors and storage capacitors areformed; an opposite substrate so arranged as to face said devicesubstrate; a liquid crystal layer sandwiched between said devicesubstrate and said opposite substrate; a first color filter formed onsaid opposite substrate; a second color filter formed on said thin filmtransistors; a reflection electrode formed on said second color filterand having an undulated shape; and openings provided in a non-effectivearea of said reflection electrode.
 2. The liquid crystal displayaccording to claim 1, wherein a normal direction on a surface of saidreflection electrode is distributed unevenly to a specific azimuth angleand a polar angle distribution of a reflection light intensity at saidazimuth angle has two or more peak values.
 3. The liquid crystal displayaccording to claim 1, wherein said undulated shape has recesses with ashape of a closed figure formed by a plurality of projection patterns ofline shapes.
 4. The liquid crystal display according to claim 1, whereinsaid openings are provided in said non-effective area of said reflectionelectrode as a transmission area, an effective area of said reflectionelectrode is a reflection area, and a potential difference between adrive voltage applied to that surface of said device substrate whichfaces said liquid crystal layer and a drive voltage applied to thatsurface of said opposite substrate which faces said liquid crystal layeris smaller in said transmission area than in said reflection area. 5.The liquid crystal display according to claim 1, wherein saidnon-effective area has a tilt angle of 0 degree to 2 degrees and/or atilt angle of 10 degrees or higher.
 6. The liquid crystal displayaccording to claim 1, wherein said openings are provided only in thatarea of said reflection electrode which overlaps that area of saiddevice substrate which passes light.
 7. The liquid crystal displayaccording to claim 1, wherein said openings are provided only in thatarea of said reflection electrode which overlaps that area of saiddevice substrate which passes light.
 8. The liquid crystal displayaccording to claim 1, wherein said openings are not provided only inthat area of said reflection electrode which overlaps saidinterconnections, said thin film transistors and said storagecapacitors.
 9. The liquid crystal display according to claim 1, whereinsaid openings are not provided only in that area of said reflectionelectrode which overlaps said interconnections, said thin filmtransistors and said storage capacitors.
 10. The liquid crystal displayaccording to claim 1, wherein a number of said openings in pixels is setfor each display color.
 11. The liquid crystal display according toclaim 1, wherein areas of said openings in pixels are set for eachdisplay color.
 12. The liquid crystal display according to claim 1,wherein a mode of a liquid crystal molecular alignment of said liquidcrystal layer is one of a homogeneous type, homeotropic type, a TN type,a HAN type and an OCB type.
 13. The liquid crystal display according toclaim 12, wherein said mode of said liquid crystal molecular alignmentof said liquid crystal layer is set in an area where said reflectionelectrode exists and an area of said openings for each area.
 14. Theliquid crystal display according to claim 1, wherein said transparentelectrode is formed on said device substrate and said reflectionelectrode is formed in contact with said transparent electrode on thatside of said liquid crystal layer.
 15. The liquid crystal displayaccording to claim 1, wherein a quarter-wave plate is provided on aliquid crystal layer side of said opposite substrate.
 16. The liquidcrystal display according to claim 15, wherein second openings areformed in that area of said quarter-wave plate which faces saidopenings.
 17. The liquid crystal display according to claim 16, whereina cholesteric liquid crystal is provided on an opposite side of saiddevice substrate to said liquid crystal layer.
 18. The liquid crystaldisplay according to claim 16, wherein a second quarter-wave plate isprovided on a liquid crystal layer side of said device substrate. 19.The liquid crystal display according to claim 16, wherein a cholestericliquid crystal is provided on an opposite side of said device substrateto said liquid crystal layer and a second quarter-wave plate is providedbetween said cholesteric liquid crystal and said device substrate.